Apparatus for testing the viscosity of liquids



July 28, 1936. Q s H LY 2,049,1 2 APPARATUS FOR TESTING THE VISCOSITY OF LIQUIDS 116] v I 112 I 112 104 101 Q I I: I

Jul 28, 1936. c. s. HEALY I 2,049,162

APPARATUS FOR TESTING THE VISCOSITY OF LIQUIDS Original Filed March 2, 1933 3 Sheets-Sheet 2 A 13 29 m L 17% VEZWYEF Jfvf/afoi 6. fieaj y.

July 28, 1936. c, s. HEALY 2,049,162

APPARATUS FOR TESTING THE VISCOSITY OF L IQUIDS Original Filed March 2, 1933 3 Sheets-Sheet 3 VEI YQF' Patented July 28, 1936 iJNlTED STATES PATENT OFFEQE APPARATUS FOR TESTING THE VISCOSITY OF LKQUIDS Clifiord S. Healy, Chicago, Ill.

2 Claims.

The present invention relates to an improved apparatus for testing the viscosity of liquids. More particularly, it has to do with determining the viscosity of lubricating oils, although, as will hereinafter appear, it may be also used to determine the viscosity, cohesion and like properties of other liquids. The present application constitutes a division of my co-pending application Serial No. 659,300, filed March 2, 1933.

One of the objects of the invention is to provide an improved viscosity testing apparatus which is capable of operation in a quick, easy and convenient manner, without requiring any special technical knowledge or training. These attributes open a field of utility which has been almost entirely neglected heretofore, namely, that of providing viscosity testing apparatus which can be used in any gasoline filling station, garage or the like, and which can be operated by any attendant, or even by the motorist himself, without requiring any technical skill. To this end, the human element, with its possible errors, has been substantially eliminated from the performance of the test so that the apparatus is almost entirely automatic in its operation, the only manual operations required being those of applying a specimen of the oil between two surfaces and applying a pressure to the oil film between these surfaces. Obviously, this represents a decided simplification over laboratory viscosimeters operating on the drip principle, etc., which require special skill in their use. Moreover, the present testing operation can be performed in but a minute or two, while the motorist is waiting, which is not true in the case of most prior I methods.

Another object of the invention is to provide a viscosity testing apparatus which will give a direct reading indication of the viscosity. For example, in the present application I have shown one embodiment employing a rotating pointer and another embodiment employing a reciprocating pointer, both of which indie-ate by direct number designation the viscosity of the speciassuming that the cooperating plate surfaces 10 preliminarily establish a definite area of film and a definite thickness of film, and establish a substantially predetermining temperature in this film, and assuming that a known pressure or pull is externally applied to one of these plate 15 surfaces, tending to separate it from the other, I have found that the length of time that this pressure or pull must be exerted before complete separation of the plates occurs is a relatively accurate measure of the viscosity of the oil. As remarked above, it is one of the objects of the invention to provide improved apparatus utilizing this principle for testing the viscosity of oils. 1

Another object of the invention is to provide a device of the above general description characterized by an improved time measuring mechanism which serves to indicate the viscosity of the oil.

Another object of the invention is to provide a viscosity testing device characterized by an improved manner of heating the plate surfaces, and controlling said heating, to the end of maintaining said surfaces at a substantially constant temperature.

Another object is to provide improved automatic controls for the machine.

Other objects and advantages of the invention will appear in the following detailed description of certain preferred embodiments thereof. In the accompanying drawings illustrating such embodiments:

Figure l is a front elevational view of one embodiment of the invention;

Figure 2 is a transverse sectional view (taken approximately on the plane of the line IIII of Figure 1) through the supporting standard, plate surfaces, spring mechanism, etc.;

Figure 3 is a fragmentary elevational View of the pressure gage for indicating the converging pressure established between the plates;

Figure 4 is a. transverse sectional view (taken approximately on the plane of the line IVIV of Figure 1) through the indicator head portion of p the device;

Figure 5 is a front elevational view of a modified construction of indicator head;

Figure 6 is a side view of the latter indicator head, partly in section;

Figure 7 is an elevational view showing the provision of an enclosing casing or oven for the plate elements;

Figure 8 is a fragmentary elevational view showing a modified arrangement for effecting heat control; and

Figure 9 is a diagrammatic view certain automatic controls. 7

Referring first to Figures 1-3, the various operating parts are preferably mounted on a support in the form of a standard I 4 rising from the base l5. At the upper end of said standard is a head portion it which carries the direct reading indicating mechanism. Projecting forwardly from illustrating the intermediate part of this standard is an arm ll which supports a refuse receptacle l8 and a lower plate element 2!. Cooperating with this lower plate element is the upper movable plate element 22, which is preferably of slightly smaller diameter than the lower plate element. The purpose of the refuse receptacle 3 is merely to collect such excess oil as may be squeezed out from between the two plate elements in establishing the film of oil between these elements. This receptacle is preferably in the form of a shallow cup-shaped pan, and may be provided with a spigot or otherdrain outlet 23b for draining an accumulation of oil from the receptacle. The lower plate element 2| is disposed centrally of the receptacle l8 and may be supported in contact therewith; although in the preferred construction I space said plate element above the bottom of the receptacle on a short spacing base 24, mainly of heat insulating material, to the end of thermally insulating the lower plate element 2! from the receptacle l8 and from oil contained therein.

Referring to Figure 2, one of the plate elements, preferably the lower element 2|, has short spacing studs 23 projecting upwardly from the top surface at three or more points for predetermining the thickness of the oil film when the other plate element is forced into contact with these studs. The height of these studs might be varied for different uses and different liquids, but

for oils of the viscosity range ordinarily used for automotive and like work I find that good results are obtained by having the studs project a height of approximately .005 of an inch. If desired, the

' upper ends of these studs may present pointed or rounded surfaces to preclude the possibility of any film of oil being maintained between the top surfaces of s'aidstuds and the bottom surface 22' of the upper plate element when said plate element is forced against said stops.

The coacting surfaces 2|, 22' of the two plate elements are preferably composed of a material such as aluminum, copper, etc., which'will be readily wetted by the oil and willhave high heat transfer for quickly heating the thin film of oil to the temperature substantially predetermined by said plate elements. Preferably, both plate elements are heated, and to this end they each include a hollow mounting portion in which is confined an electrical heating element 26. For maintaining these devices at a substantially constant temperature, each includes athermostatic control switch 21 preferably disposed adjacent to the center of the disk-shaped 7 plate element. These thermostatic control switches are well known devices and need not be illustrated or described in detail. When the machineisto test automobile engine oils, these thermostatic switches are set to maintain the plate elements 2| to 22 at a temperature corresponding to some oil temperature in the engine, such as the average crank case temperature under operating conditions.

The feed wires connecting with the heating element in the lower plate element 2! may extend down through the spacing post 24 and through the arm IT in passing back into the standard l4; and the feed wires connecting with the heating element of the upper plate element preferably extend therefrom to the standard M in the form of a flexible connection 28 which permits the upper plate element to be raised and lowered. In a later embodiment I shall hereinafter describe how a single thermostatic switch may be arranged to control the temperatures of both plate elements.

The upper blade element 22 is secured on the lower end of a reciprocable plunger 3| which is guided for vertical movement in an upper arm 32 also projecting forwardly from the standard M. Referring to Figure 2, this upper plate 22 has a universally rockable mounting on the plunger 3|, afforded preferably by a substantially spherical or pointed head'member 33 on the rod arranged to seat against a substantially spherical or rounded surface 34'formed in the boss 35 projecting up centrally from the plate element. A

gland nut 36 screws down into the boss 35 and presses against the top side of the head 33, the reduced plunger extension am having a relatively loose fit in the bore of said gland nut -to accommodatethe slight rocking of the plate relatively to the plunger. This mounting of the upper plate element insures that said plate element will always contact uniformly with the several spacing studs 23 in predetermining a film of oil of uniform thickness between the plates.

The supporting arm 32 is hollow and the plunger 3| extends through the top and bottom walls thereof. Fixedly secured in the lower wall is a depending tubular guide 38 surrounding the plunger and having a threaded upper end 38v within the supporting arm 32. A nut 39 screws down over the threaded end 38' to press against the top side of the bottom wall of said supporting arm for securing the tubular guide 38 in place. An adjacent nut 41 also screws down over the threaded end 38 of the guide. The latter nut serves as an adjustable bottom stop for a compression spring 42 which surrounds the plunger within the arm 32. Access to these parts is afforded by a removable front plate 43 which is secured over the open front end of the hollow arm 32 by screws 44. The upper end of the spring 42-thrusts upwardly against a collar 46 which abuts against the nut "41, screwing downwardly top wall ofthe hollow arm 32 by screws 55 and carrying stationary and movable contacts56 and 5-1. The switch actuating member 58 is pivotally supported between the top and bottom insulating pla'tes andhas "a forkedend in which engages over the reduced threaded end 3lb of the plunger rod. A-cushioning washer 48 may be disposed the-projecting arm of the switch operating member 49. The other end of the member 58 is adapted to swing upwardly and press the movable-contact 51 against the stationary contact 56 when the plunger 3| moves downwardly. A ten sion spring 59 is extended between a pin on the member 58 and a fixed point of anchorage in 'such'relation as to exert a biasing action on the member 58 for imparting a snap motion thereto in either direction of movement.

In the embodiment above described, after a specimen of the oil has been spread out on the lower plate 2|, the upper plate is forced downwardly against this oil by the exertion of downward pressure on the upper knob 6|. The downward pressure exerted on this knob must be sufiicient so that, irrespective of the viscosity of the oil, the upper plate will be forced down into contact with the studs 23. As previously remarked, these studs insure that all oils will be tested at the same thickness of film between the plates, and it will be evident that when an oil of relatively heavy viscosity is inserted between the plates it will require a greater pressure to bring the upper plate down against said studs within a reasonably short space of time than it would require with a lighter viscosity of oil. It is within the scope of my invention to have the knob 6| connected as a rigid part of the plunger 3| so that the pressure imparted to said knob is transmitted directly to the upper plate. In this case, however, dependence would be placed upon the operator always exerting a sumciently heavy downward pressure on said knob adequate to overcome the opposing pressure on the lifting spring 42 and also to exert the necessary downward pressure on the oil to bring the upper plate against the studs 23, irrespective of the viscosity of the oil. This introduces a source of possible error, because, if the operator did not exert sufficient downward pressure to bring the upper plate into contact with the studs against a heavy body of oil, the reading of that test would likely be erroneous. Accordingly, I have found it desirable, although not essential, to interpose a pressure gauge between the knob BI and the plunger 3| which will indicate the downward pressure being exerted 'on the'knob, whereby to insure that this pressure is adequate in view of the apparent viscosity of the oil. This pressure gauge, generally designated 62, comprises a sleeve 63 screwing down over the externally threaded upper end of the nut 41 and having a reduced upper end in which is guided the stem 64 of the knob. A head 65 on the lower end of this stem is arranged to cooperate with two compression springs 66 and 61 confined within the sleeve 63. The lower end of the outer spring 66 abuts against the top of the nut 01, and the lower end of the inner spring 61 abuts against the shouldered outer head of the adjusting screw 68 which threads down into the plunger 3|. Threading the latter screw upwardly or downwardly (with the sleeve 63 removed), is operative to adjust either the pressure that the inner spring normally exerts against the head 65 or the distance which this head must move downwardly before encountering the inner spring. A stud 1| projects laterally from the head 65 through a vertical slot 12 in the sleeve 63 and carries the pointer 13, which cooperates with pressure graduations 14 (Fig. 3) marked down along the sides of the slot 12. These markings are so graduated that when the pointer 13 is designating 40, the above 7 described spring arrangement is exerting sufficient downward pressure to overcome the lifting spring 42 and to transmit, in addition, suflicient force to the upper plate 22 for causing-this plate to move downwardly against the studs 23 in a rather brief interval of time against oil having a body corresponding to S. A. E. 40-and, of course, other in dications on the pressure gauge will also do the same with other oils of corresponding viscosity. Thus, the provision of the pressure gauge insures that the attendant will exert at least a sufficient degree of downward pressure on the knob 6| to promptly bring the upper plate element down against the studs 23.

Referring now to the indicator head portion I6, it will be seen from Figures 1 and 4 that this portion of the device comprises a circular or polygonal casing 8| enclosing a numbered dial 82 and rotating pointer 83 cooperating therewith. The major scale graduations 82a are designated 10-2030, et'c., corresponding to S. A. E. designations of different viscosities. The front of the casing 8| is closed by a'glass plate 85, suitably confined between the front marginalflange 86 and bracket clips 81 engaging the backside of the glass and secured to the housing. The operating parts preferably have unit assembly upon a back plate 88 which is removably secured at the rear end of the housing, as by screws 89 threading into a flanged ring 9| secured to the housing. A yoke-shaped supporting member 92 has attaching portions 92a secured by screws 93 to the back plate 88, and secured to the vertical front bar portion 92b thereof is the dial disc 82. The shaft 95 carrying the pointer 83 is journaled be provided for by splining' both the shaft and sleeve, or forming both of polygonal cross-section. The sleeve 99 extends through the supporting plate 96, in which it has rotatable and slidable support, and the cylindrical rear end of the shaft I0| is journaled in a bearing bracket I02 secured to the supporting yoke 92. The rear end of the sleeve 99 terminates in a thrusting collar I03, and a compression spring I04 is confined between this collar and the back side of the supporting plate 96, the action of. this spring being normally to hold the pinion 98 in mesh with the spur gear 91. The pinion can be shifted out of mesh with the gear through the actuation of a bell crank lever I05, which is pivotally supported on a pivot bracket I06 secured to the mounting member 92. One arm of this bell crank lever is forked to transmit thrusting motion to the collar I03, and the other arm has a pull cord I01 extending downwardly therefrom and terminating in a ring or other pull member I08, thelatter depending from the bottom of the housing 8| As will hereinafter appear, downward pulling of the member I08 is operative to releasethe pinion 98 from the gear 91 for the purpose of permitting the pointer 83 to be restored to its initial or normal position.

A friction slip clutch. I09 operatively connects .worm'wheel H] is driven by afvi' jorm H2 mounted on the shaft 30f an electric motor H4, the latter being supported in any suitable manner on the mounting member 92. It, is desirable that the pointer 83 rotate in anzapproximately fixed time relation, and;accordingly, where alternating current is available I preferably employ as the motor I M a self-starting synchronous motor operating in time phase with the current, which insures that in successive operations the pointer will be passing successive graduations 82a in the same time intervals. However, direct current motors and universal motors can also be employed with substantially equal efiectiveness, because the torque load is approximately constant at all times. In order to assure immediate stopping of the motoras soon as its current supply is interrupted; by, the switch 5!, there is provided a friction brake arm H6 which bears against a collar drum H! of the motor shaft. It will be understood that other forms of speed reducing gearing may be employed in lieu of the worm gearing H1, H2. 'In the resetting operation, as soon as the pinion 98 is shifted out of mesh with the gear 91, the pointer is swung back to its initial position by the action of. a spiral spring I I8. The upper end of this spring is secured to a stud H9 projecting laterally from the gear 91, and the inner end of this spring is secured to a stud I2 I projecting inwardly from the mounting member 92. A stop pin I22 proje'otsfrom the hub of the gear 91 and is adapted to engage the stud l2! for stopping the resetting motion of the pointer with the latter in registry with itsinitial or normal position. The face of the dial 82 may be illuminated by an electric light bulb I24, which has its socket secured to a bracket I25 mounted on the'upper portion of the dial. A suitable switch in the circuit of this bulb may be arranged to be controlled by a pull cord I26 hanging down through the bottom of the housing and having a ull ring I21 at its lower end. All of the parts above described can be removed as -a unit assembly along with the back plate 88 by the simple disconnection of. the pull cords and the electrical conductors.

The switch 5| is connected in series with the circuit of the motor I [4, which circuit is conventionally represented by the conductors I31, l3'la, so that the motor starts and stops with the closing and opening of the switch contacts56, 51.

' The operation of this, embodiment is as follows:

Aspeci'men of the oil is placed on the lower plate 21 with a s'uflicientquantity to form the required thickness of film over the entire area of the plate. In this regard, while the full line position of the upper plate 22 indicates its normal position in which it is normally. held by the spring 42, this upper plate can be raised to an elevated position substantially as indicated in dotted lines, in order to afford more convenient access to the surfaces of the plates. For raising the upper plate, the operator merely pulls upwardly on the knob B I, thereby sliding the plunger 3] upwardly through the collar 46 and elevating the stop nut 41 from the top of said collar. The engagement of said stop nut against the top of said collar determines the normal position of the upper plate. Both plates have previously been heated by a passage of current through their heating elements 26 and are now at, the

normal temperature maintained by the thermostatic control switches 21. In practice, I have foundigood resultsto be obtained by maintaining lower plate 2|, theknob BI is now thrust downwardly to bring the top plate 22 down against this oil. By observing the pressure gauge 62 at this time, the operator is assuredthat he is exerting-a' suflicient downward pressure commensurate with the apparent thickness of the oil; there is nogobjectionto exerting a greater pressure than is actually necessary, the pressure gauge 62 serving primarily to indicate that suflicient pressureiis being exerted to force the upper plate 22:down against the studs 23 within a relatively short timeinterval. As soon as the operator presses downwardly on the knob 6|, the motion which he transmitted through the plunger rod 3| effected the closing of switch 5|. This immediately started themotor H4 to rotating and consequently the indicator arm 83 starts moving from its initial point 82b to the start test: position 820. The operator holds the knob 6| pressed downwardly during the time interval that the pointer is moving between these two points. This time inte'rvalis several seconds, or oi sufficient duration to insure, first, that the upper plate 22 will be'forced againstthe studs 23 and, second, that the relatively thin film of oil thus predetermined between the two plates shall havebeen heated substantially to the temperaaure of the plates. At the instant that the pointer arm 83 reaches the start test{ position 820, the operator releases the knob 6|. Thereupon, the testing time interval starts, during which the two plates are subjected to the relative separating pressure exerted by the predetermined pressure of the spring 42, which separating pressure is resisted by the surface tension and cohesion of the oil film. During this time, the switch 5], of course, remains closed because of the loweredposition of the plunger 31 and plate 22, and consequently the indicating pointer 83 continues its rotative movement. Observation-of the action taking place between the plates indicates that the adhesion'or surface tension between the oil film and the plates maintains the film at a more or less constant area until a time near the midpoint or approaching the end of the test interval. With the gradual separation of the plates, the concave meniscus recedes inwardly around the body of oil, with the result that the specimen is constantly changing shape or reducing its effective area as viewed'in plan. That is to say, the horizontalarea of the body of oil decreases and its vertical depth increases. During this gradual slight separation of theplates, the spring pressure is being resisted by the adhesion of the oil to the plates and by the cohesion of the intervening body of oil between the plates. Finally, when the eifective area of the body is reduced to the point where it can not sustain the separating tension exerted by the spring 42, rupture of the body occurs and. the upper plate 22 snaps upwardly. This opens the switch 5! and the motor I I4 immediately stops. The position of the pointer arm 83 at this time is an indication of the viscosity of that specimen. Preparatory to testing any other specimen, the pointer is restored to its the like.

tion. The casing 8| is of triangular or rectangular cross-section, and at one face is provided with a vertically arranged scale or scales 82'. The indicator 83 consists of a transverse pointer secured to the upper end of a rack bar I34. The upper end of said rack bar carries a guide block I35 which slides in a guideway defined by two spaced vertical bars I36, and the pointer 83 may be secured to this guide block. The front glass 85' covers the pointer and scales. The lower portion of the rack bar extends downinto the hollow standard I4 and is suitably guided to mesh with a spur gear I31. This gear is one of a train of gears I38, I39, I4I, I42, andaworm wheel III", all of which are disposed'between two spaced frame plates I43, in which plates the shafts of said gears are joumaled. The worm wheel III is driven by the worm 2' on the shaft II3 of the motor I I4? and a friction brake I I6 bears against the friction surface of the motor shaft, substantially as previously described. The gear I38 is arranged for sidewise shifting into and out of mesh with the gears I31 and I39, being secured to a shaft I44 which is slidably mounted in the frame plates I43. A leaf spring I45 is'secured to one of these frame plates and has its end abutting against the adjacent .end of said shaft, whereby to normally hold the gear I36 in mesh with its companion gears. A bell crank lever I46 is journaled in a bearing bracket I41, mounted'on the opposite frame plate, and one arm of this lever extends downwardly to abut against this end of the shaft I44. A tripping link I48 has its upper end hooked to the other end of said bell crank lever and extends downwardly through the bottom of the housing, where it terminates in a pull eye I49. Pulling down on this tripping member shifts the gear I38 out of mesh and permits the rack bar I34 and pointer 83' to drop down to the normal or initial position. The scales may be translucent for illumination by an electric light I24 disposed within the housing and controlled by av pull connection I26 The operation'of this embodiment of indicator head will be manifest from the preceding description. Should theviscosity of the oil exceed the maximum reading, of the machine, the spur gear I31 will merely run off the lower end of the teeth on the rack bar I 34, the bar being provided with a blank space for this purpose.

Referring-to Figure 'I, it may be desirable to enclose the plate elements within a housing or oven I52 in order to prevent fluctuations of heat in the plate elements, particularly when the machine is disposed outdoors or in a drafty location... This housing can be secured between the two armsI1 and 32 projecting forwardly from the standard, with the housing enclosing the drip pan I8, both plate elements, and the lower portion of the plunger 3|. A hinged door I53 normally closes a relatively large opening in the front of the housing, through which access may be gained for placing the oil between the plate elements and for cleaning the plate elements.

Figure 8 illustrates a modified temperature controlling arrangement. Inserted in one of the plate elements, preferably the lower one, is a sealed bulb I54 containing a suitable temperature responsive fluid, such as ether, mercury, or A small tube I55 extends from this bulb to an automatic switch I56'which contains a pressure responsive element responding to the rise and fall of pressure transmitted from the bulb I54 through the tube I55. This type of switch is old and well known and no detail disclosure thereof is necessary, it being suflicient to state that a rise of fiuid pressure with increasing temperature is operative to open the switch and a lowering of pressure with a decrease of temperature is operative to close the 5 switch. In such arrangement, the two heating elements of the upper and lower plates are connected together in series so that both plates receive the same current over the same time intervals determined by the switch I56. This series circuit arrangement is diagrammatically illustrated in Figure 8.

In Figure 9, I have diagrammatically illustrated certain automatic controls which may be embodied in the machine. One of these is an automatic latching arrangement which maintains the downwardly acting spring pressure on the plates and on the oil film until the pointer of the indicating head reaches the start test position, whereupon this latch is automatically 20 tripped. for releasing the downwardly acting pressure and permitting the upwardly acting pressure of the spring 42 to become effective. The latter spring is confined between the adjustable nut 4I and a suitable collar or shoulder 49a on 253 the plunger. The plunger continues above this collar and is provided with an upper guide collar NH and is also provided with a reduced threaded end I62. The collar I6I guides the vertical movement of the lower end of the enclosing sleeve 63a, and the threaded stud I62 screws into a stem I63 extending up into said sleeve. The sleeve has an annular groove I64 formed therein, and the stem I63 is provided with a head I65 which is operable to engage the upper side of the internal shoulder formed within the sleeve by said groove. A compression spring 66a is confined between the head I65 and the closed upper end of the sleeve. The sleeve 63a. may be of any suitable two-part construction to permit assembling the stem I63 and spring 66a therein. The upper end of said sleeve carries the plunger knob am. This construction can be carried by the upper, forwardly extending arm 32, the same as previously described. Mounted within said arm is a latch I61 which is normally thrust against the lower portion of the sleeve by a spring I68. When the knob 6Ia is pressed downwardly through its intended range of move. ment, the annular groove I64 is moved down into the plane of the latch I61, which is immediately projected into said groove for preventing return movement of the sleeve 63a. The sleeve is held in this depressed position until the pointer of the indicator head arrives at the fstart test position 820, and at this instant a circuit is closed which releases the latch I61. The main supply wires are indicated at I" and fl,12,and the pointer arm is electrically connected with one of these circuit wires through 60 a wire I13 and any suitable brush arrangement coacting with the pointer. At the start test position 820, a contact I14 has insulated mount:

ing in the dial, and the pointer arm carries a suitable clip or contacting element to engage 65 with said contact I14 when the pointer is in this position. Such completes a circuit extending through wire I15 to one side of a solenoid coil I16, and from the other side of this coil through wire I11 to the other supply wire I1I'. The sole- 70 noid coils attracts a core I18 which is operatively connected with the latch I 61. This operative connection may be a direct connection as shown, or it may include any desired power multiplying arrangement. The energization of the solenoid withdraws the latch I81 fromthe groove I64 and permits the sleeve 63a to snap upwardly, thereby relieving the plunger of the downward pressure of the spring 660., and starting the test with the plunger only subjected to the lifting pressure of the lower spring 42. Itwill be seen from the foregoing that in this arrangement it is only necessary that the operator press downthe plunger head Bla sufficiently far to cause engagement of the latch I 81 in the groove I64, whereupon the subsequent operation of releasing this downwardly acting spring pressure is automatically performed precisely at the proper time in the motion of the pointer arm. The spring 66a is proportioned so that this range of movement of the sleeve 63a will always exert sufiicient additional pressure on the upper plate element for quickly predetermining the thickness of the oil film, irrespective of the viscosity of the oil being tested. This automatic spring tripping function can be embodied in any of the constructions previously described.

In Figure 9 I have also illustrated another automatic control feature which serves to make the starting of the electric motor in the indicator head responsive to the establishment of the predetermined thickness of oil film. In this construction, the spacing studs 23-are electrically insulated from the lower plate 21 and, for cooperation therewith, the upper plate 22 is provided with a companion set of studs or contacts 23a, also electrically insulated from their plate 22. For clarity of illustration, these studs or contacts 23, 23a have been shown in enlarged proportions in Figure 9. When all of the companion pairs of studs or contacts are in abutting contact, at which time a predetermined thickness of oil film has been established, a series circuit is completed through wires I82 and I83. The manner in which these several pairs of contacts are connected together in series is clearly illustrated. The wire I82 conducts current from the supply wire I H and the wire I83 connects with one side of a solenoid coil I84. The other side of this solenoid coil is connected through wire I85 with the other supply wire I12. It will thus be seen that at the instant that all of the spacing studs and their associated contacts are in engagement, predetermining a definite thickness of oil film, the solenoid coil I84 will be energized. This attracts a core I86 which is operatively connected with a switch arm I81, pivoted'at I88. Theother end of said switch arm carries a movable contact I9I which is swung into engagement with a stationary contact I92 upon the energization of the solenoid coil I84. The engagement of said contacts completes acircuit through wires I93 and I94 connecting the one side of the motor i I4, the other side of said motor being connected with the other supply wire I12. It will thus be seen that the starting of said motor is dependent first upon the body of oil having been reduced to a film of predetermined thickness, such aiding in minimizing the effect of possible variables intesting oils' of widely different viscosities. A biasing spring I96 is operatively connected with the switch arm I81 whereby it swings to an over-center position with regard to the pivot I88 for yieldingly holding the switch arm in either its closed or open position. Hence, with'the spacing studs 23 and their contacts 23a separate in the gradual raising of the upper plate, prior to the" complete disruption of the oil film,the resulting interruption of the series circuit through the wires I82 and I83 will not separate the switch contacts I9I and I92, which willbe yieldably held in their closed position by the spring: I 96, thereby insuring continued operation of the motor II 4. However, as soon as the oil film breaks, the collar 49a snaps upwardly with the plunger and with the upper plate and strikes 5 the projecting end of the switch arm I 81 for throwing this switch arm to open circuit. position, thereby stopping the motor I I 4. The spring I96 then holds the switch arm in this open circuit position until the solenoid I84 is again enerl0 gized in the performance of another testing operation.

If desired, an. electrically operated limit control may also be associated with the switch I81, so that the motor circuit will be automatically opened 15 when the indicating pointer reaches the maximum position. This would avoid the necessity of any slip clutch, described in connection with Figure 3, or of the pinion running oil the end of the rack bar, described in connection with Figure 5. In this automatic limit control, a contact I 91 has insulated mounting in the dial or gauge plate of the indicator head in position 'to be engaged by the same contact element on the pointer arm which engages the contact I14. This contact I91 25 is positioned at the maximum limit of movement of the pointer arm. A wire I98 extends from said contact to one side of a solenoid coil I99,'and extending from the other side of said coil is a wire 2III which connects with the supply wire I1I A core 202 in said solenoid coil is operatively connected With the switch arm I81 on the other side of the pivot I88, whereby energization of the coil I99 is operative to separate the switch contacts I9I, I82. It will thus be seen that should the viscosity of the lubricant exceed the capacity of the machine, the motor circuit will be automatically opened when the pointer arm reaches its maximum position in engagement with the contact I91. It will be evident that the two control contacts I 14 and I 91 can be appropriately arranged in the vertically disposed scales 82 of the embodiment disclosed in Figures 5 and 6, in adapting these control functions to that construction.

The initial calibration of the machine and any subsequent adjustments thereof may be easily efiected by screwing the adjusting not H upwardly or downwardly to vary the effective pressure of the lifting spring 42. Ifdesiredany suitable seal or look may be associatedwith the removable plate 43 over the end of the arm 32 for preventing unauthorized access to this adjusting nut. As previously remarked, I have found it desirable to make the lower plate of slightly larger diameter than the upper plate, but this is not essential. Thin oils when heated to the temperature predetermined by. the plates have a tendency to run, and by making the lower plate larger the outside quantity of oil on this lower plate tends to restrict downward flow of the oil film which is defined directly between the plates. This outer ring of oil isof definite volume around the parting line between the plates and may maintain the oil seal for a larger time interval. When the downward pressure transmitted through the springs 66, 61 and 66a is released, it may be desirable to provide suitable motion retarding or cushioning means so that the recoil from such spring or springs shall not transmit upwardly acting shock to the top plate 22. For example, in Figure 9, the springpressed ball 204 pressing against the sleeve 63a, is conventionally representativeof a frictional or other suitable motion retarding or cushioning 7o means for this purpose. The time graduations on the indicating head can, if desired, be made to correspond to seconds or some unit of time closely approximate thereto, such being largely determined by the areas of the plates 2|, 22 and by the pressure established in the spring 42.

For example, a reading of S. A. E. 40 might be arranged to correspond to 40 seconds. In the operation of the machine, the plates predetermine a body of oil of predetermined cross sectional area and predetermined thickness, and as soon as the spring 42 becomes efiective, tending to separate the plates, this body starts to change shape, atmospheric pressure and endwise tension between the plates resulting in the body diminishing in cross sectional area and increasing in thickness, until the cohesion in the reducing cross sectional area fails to sustain the separating force, whereupon the body is disrupted and the top plate quickly moves upwardly. Should difierences in atmospheric pressure at difierent localities result in any appreciable variation of readings, the scale indicia or the pressure of the spring 42 may be appropriately adjusted to these difierences.

While I have illustrated and described what I regard to be the preferred embodiments for carrying my invention into efiect, nevertheless it will be understood that such are merely exemplary and that numerous departures may be made therefrom within the broad scope of the invention. Furthermore, while the principal utility of the invention would apparently reside in the testing of the viscosities of lubricating oils, nevertheless the invention may also be employed in other fields for testing the viscosity, cohesion, adhesion, or like properties of other liquids and semi-liquid materials.

I claim:

1. Apparatus of the class described comprising two surfaces adapted to receive a specimen of the liquid therebetween and arranged for relative converging motion to establish a film of the liquid between said surfaces, and arranged for relative separating motion to test the resistance of said film to said separating motion, means 0perable to cause said converging motion, means creating a force tending to cause said relative separating motion, an electrically operated time indicating device for measuring the time interval that the film resists said separating motion, a control circuit for said device, and contacts carried by said surfaces governing the circuit controlling said indicating device.

2. Apparatus of the class described comprising two surfaces adapted to receive a specimen of a liquid therebetween and arranged for relative converging motion to establish a film of the liquid between said surfaces, and arranged for relative separating motion to test the resistance of said film to said separating motion, means operable to establish a pressure to cause said converging motion, an electrically operated time indicating device having a control circuit, contacts in said control circuit carried by said surfaces, and operative to initiate the starting of said device as soon as the surfaces have been converged, and pressure creating means tending to cause said separating motion, said time indicating device having means to indicate a predetermined lapsed interval from the starting of said device and the beginning of the time interval that the film resists the latter pressure creating means.

CLIFFORD S. I-IEALY. 

